SMP100LC

5/10

APPLICATION NOTE

In such a stage, parallel function is assumed by one or several Trisil, and is used to protect against short

duration surge (lightning). During this kind of surges the Trisil limits the voltage across the device to be

protected at its break over value and then fires. The fuse assumes the series function, and is used to pro-

tect the module against long duration or very high current mains disturbances (50/60Hz). It acts by safe

circuits opening. Lightning surge and mains disturbance surges are defined by standards like GR1089,

FCC part 68, ITU-T K20.

Figure 8: Variation of thermal impedance

junction to ambient versus pulse duration

(Printed

circuit

board

FR4,

SCu=35µm,

recommended pad layout)

Figure

9:

Relative

variation

of

junction

capacitance versus reverse voltage applied

(typical values)

In wireline applications, analog or digital, both central office and subscriber sides have to be protected.

This function is assumed by a combined series / parallel protection stage.

1E-3

1E-2

1E-1

1E+0

1E+1

1E+2

5E+2

1

10

100

t (s)

p

Z/R

th(j-a)

th(j-a)

C [V ] / C [V =2V]

RR

12

5

10

20

50

100

300

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

V (V)

R

F =1MHz

V= 1V

T = 25°C

j

RMS

Line

Ring

relay

Line

Ex. Analog line card

Ex. ADSL line card or terminal

Fuse TCP 1.25A

T1

T2

SMP100LC-xxx

Typical circuit for subscriber side

Fuse TCP 1.25A

Tip S

Gnd

SMP100LC-xxx

Ring S

SMP100LC-xxx

Fuse TCP 1.25A

Tip L

Gnd

Ring L

Typical circuit for central office side